In autumn 1978 some “strange phenomena” were noticed along a section of continental shelf off Marche and Abruzzi coasts. A fishing boat sank with two fishermen dead, up to tens of meter height water columns rising, dark masses coming up from the seabed, wakes of small air bubbles spreading over the sea level as they were some traces of invisible submarines, light red–coloured “luminous trails or lightning” travelling through the atmosphere from the sea to disappear suddenly. The organic matter transformed into gas affects the environment, fishermen’s work, engineering operations (installation of wharf and platform for hydrocarbons, etc.) and tourism. These gas seepages are particularly abundant in the Adriatic Sea.